The present invention relates generally to automatic projectile firing weapons. More particularly, the invention relates to a method and apparatus for absorbing the recoil force of an automatic projectile firing weapon.
In many combat situations, a lightweight, easily portable automatic weapon that is capable of accurately firing a projectile over a significant distance would provide a decisive tactical advantage. There are many existing small and medium caliber automatic weapons that are specifically designed to fill particular combat needs. However, weapons that are effective at ranges of up to 2,000 meters, for example the 0.50 caliber M2 heavy machine gun and the 40 mm Mk-19 grenade, are too bulky and heavy to be easily portable. Other automatic weapons, like the 7.62mm M60/M240 medium machine guns and the 5.56 mm M249 squad automatic weapon, are easily portable but are not effective at long ranges.
The accuracy of a weapon at a long range is dependent upon the ability of the weapon to manage the recoil force of the fired projectile. The magnitude of the recoil force is a function of the mass and velocity of the projectile which directly effects the expected travel distance (range) of the fired projectile. As the expected range of the weapon increases, so does the magnitude of the recoil force. Weapons designed to fire projectiles over a significant distance typically have a greater weight than weapons designed to fire projectiles over a shorter range. The greater weight is necessary to restrain the more energetic cartridges, absorb the increased recoil force, and prevent the recoil force from disrupting the accuracy of the weapon.
To reduce the weight of a weapon that is accurate over a significant range, an improved method of handling the recoil force must be found. Many attempts have been made to manage the recoil force beyond the typical short recoil cycle or gas operated bolt cycle. In some designs, a counterweight is attached to the recoiling mass of the weapon to absorb the recoil energy. In other designs, a spring is used to absorb and store the recoil force. The energy stored in the spring or counterweight can then be used to move the recoiling mass forward when the next projectile is fired. The forward momentum of the counter-recoiling mass will partially absorb the recoil force of the next projectile.
However, these designs fail to account for the recoil force resulting from the first projectile. Because the first projectile is fired when the weapon is in a resting state, the only resistance to the initial recoil force is the spring or counterweight. This results in a higher load on the recoil system when the first projectile is fired as compared to subsequent shots. In a tripod mounted weapon, this higher load lifts the front leg of the tripod higher off the ground, which will disrupt the accuracy of at least the first few projectiles of a burst. The higher load also causes instability in the gun/mount system, which may only be corrected by increasing the amount of ballast in the system.
After a transient period, the weapon and mount will overcome the recoil overload and achieve a steady state dynamic recoil action. If the weapon is flexibly mounted, it is likely the weapon will not become accurate and effective until the transient period is passed and the weapon enters this steady state recoil action. However, during the transient period, several projectiles are wasted before the weapon settles into the steady state recoil action. Furthermore, due to mount flexibility, a steady state recoil action can have significant effects on accuracy.
In light of the foregoing there is a need for an automatic weapon that minimizes the effect of the recoil force of both the initially fired rounds and all subsequent rounds.
Accordingly, the present invention is directed to an automatic projectile firing weapon that obviates one or more of the limitations and disadvantages of prior art automatic projectile firing weapons. The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention is directed to an automatic projectile firing weapon. The weapon includes a receiver that has a main sear and a trackway. A barrel assembly is slidably mounted in the trackway and is moveable between a rearward position and a forward position. The barrel assembly is engageable with the main sear at the rearward position. A firing position is located between the rearward position and the forward position and preferably closer to the forward position. There is provided an operating spring connected between the receiver and the barrel assembly. The operating spring biases the barrel assembly towards the forward position. There is also provided a manual retracting device that moves the barrel assembly rearwardly into engagement with the main sear, thereby compressing the operating spring. A trigger is provided to release the main sear and allow the operating spring to move the barrel assembly forwardly along the trackway of the receiver. There is further provided a buffer connected between the receiver and the barrel assembly to dampen the velocity of the barrel assembly to prevent the barrel assembly from exceeding a predetermined maximum velocity when a round is fired. The recoil energy from the fired round is absorbed in part by the forward motion of the barrel assembly and in part by the operating spring. The recoil force felt by the receiver is that of the operating spring and, in part, the buffer.
In another aspect, the invention is directed to a method of absorbing the recoil force of a projectile firing weapon. The weapon includes a barrel assembly slidably mounted in a receiver and an operating spring connected between the receiver and the barrel assembly. The method involves compressing the operating spring by retracting the barrel assembly within the receiver to engage the barrel assembly with a main sear when the operating spring is fully compressed. The main sear is released to allow the operating spring to bias the barrel assembly forwardly within the receiver. A round is chambered as the barrel assembly moves forwardly along the trackways. The forward motion of the barrel assembly is buffered to prevent the barrel assembly from exceeding a predetermined maximum velocity. The round is fired when the barrel assembly reaches a predetermined location in the receiver. The recoil force of the fired shot reverses the motion of the barrel assembly to move the barrel assembly rearward and re-compress the operating spring. The buffer is configured to maintain a nearly constant dynamic condition of the barrel assembly during the firing and recoil portions of the operating cycle so that effects of varying friction, weapon attitude, and cartridge impulse on the weapon operating cycle are minimized.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.